The Cognitive Ecology of Animal Movement: Evidence From Birds and Mammals

Cognition, defined as the processes concerned with the acquisition, retention and use of information, underlies animals’ abilities to navigate their local surroundings, embark on long-distance seasonal migrations, and socially learn information relevant to movement. Hence, in order to fully understand and predict animal movement, researchers must know the cognitive mechanisms that generate such movement. Work on a few model systems indicates that most animals possess excellent spatial learning and memory abilities, meaning that they can acquire and later recall information about distances and directions among relevant objects. Similarly, field work on several species has revealed some of the mechanisms that enable them to navigate over distances of up to several thousand kilometers. Key behaviors related to movement such as the choice of nest location, home range location and migration route are often affected by parents and other conspecifics. In some species, such social influence leads to the formation of aggregations, which in turn may lead to further social learning about food locations or other resources. Throughout the review, we note a variety of topics at the interface of cognition and movement that invite further investigation. These include the use of social information embedded in trails, the likely important roles of soundscapes and smellscapes, the mechanisms that large mammals rely on for long-distance migration, and the effects of expertise acquired over extended periods.

Ultimate regulation of fecundity in species with precocial young: declining marginal value of offspring with increasing brood size does not explain maximal clutch size in Black Brent geese

Lack 18:125-128 (1967) proposed that clutch size in precocial species was regulated by nutrients available to females during breeding. Drent and Daan 68:225-252 (1980) proposed the individual optimization hypothesis, whereby individual state determines the optimal combination of breeding date and clutch size. Neither hypothesis accounts for variation in nutrients among females at the end of egg laying, strong right truncations in clutch size distributions, or the fact that many species with precocial young are determinate layers. One solution is that there is a maximum clutch size, above which the number of fledged young declines. We manipulated brood size in Black Brent geese to decouple brood size from maternal quality and produce broods larger than the natural maximum. We recaptured marked goslings to assess variation in prefledging survival as a function of brood size and we estimated relative prefledging survival of goslings using a Bayesian hierarchical approach. We considered effects of natural clutch size, brood size and their interaction on probability that we captured goslings at about 4 weeks of age. Prefledging survival declined with increasing brood size ([Formula: see text] = -0.53; 95% CI -0.91 to -0.16), while laid clutch size had little influence on prefledging survival ([Formula: see text] = -0.04; 95% CI -0.42 to 0.32). Despite declining per capita survival with increasing brood size, the most productive brood size was six goslings, which is greater than the typical maximum clutch size of five. Thus, reduced survival in large broods, by itself, is not the sole mechanism that limits maximum clutch size. We suggest elsewhere that incubation limitation and lower residual reproductive value for females tending larger broods may be other mechanisms limiting maximal clutch size in brent.